Mobile data communications is evolving quickly because of global communications network such as the Internet, intranets, laptops, PDAs (personal digital assistants) and increased requirements of workforce mobility. Third generation mobile system (3G) technologies (e.g., UMTS-Universal Mobile Telecommunications System) are considered enhancements to GSM (Global System for Mobile telecommunications) cellular standards.
New technologies are required to deliver high speed location and mobile terminal specific content to users. The emergence of new technologies thus provides an opportunity for a boom similar to what the computer industry had in 1980's, and that Internet and wireless voice had in 1990's. UMTS can be considered as the commercial convergence of fixed line telephony, mobile, Internet and computer technology. The UMTS transport network is preferred when handling demanding wireless data traffic.
To further extend and/or improve the performance of existing UMTS protocols a collection of mobile telephony protocols are utilized, such as HSPA (High Speed Packet Access). Typically, voice calls can be routed over HSPA based transport channels, such that, network air interface (Uu) and RNC (radio network controller) and/or NodeB transport efficiencies can be increased. Further, carrying CS traffic over HSPA can significantly save power and conserve battery life of the UE (user equipment).
As UMTS and other 3G technologies evolve towards facilitating voice (and video) over packet switched transport mechanisms, such as VoIP (Voice over Internet Protocol), various problems to carry voice traffic over a packet switched interface can be encountered. Carrying CS traffic over HSPA reduces priority in the IuB interface. Further, during CS over HSPA, effective coverage area can be reduced due to loss of SHO (soft handover) in the downlink.